Causes of Petechial Rash - Differential Diagnosis Algorithm



Pinpoint areas (less than 2 mm) of hemorrhage, which are reddish-purple lesions called petechiae.



Petechiae Etiology:

 • Abnormalities in primary or secondary hemostasis:

	- Thrombocytopenia

	- Abnormal platelet function

	- Clotting factor deficiency

	- Abnormal clotting factor function

 • Disruptions in vascular integrity:

	- Trauma

	- Infection

	- Vasculitis

	- Collagen disorders



Petechiae Red Flags:

 • Fever

 • Toxic appearance

 • Hypotension

 • Mucosal lesions

 • Severe pain

 • Extremes of age

 • Immunosuppressed

 • New medication



Febrile, Toxic Patient:

 • Palpable Rash:

	- Meningococcemia

	- Disseminated gonococcal infection

	- RMSF

	- Henoch Schonlein Purpura

	- Endocarditis

 • Non-Palpable Rash:

	- Purpura fulminans

	- DIC

	- TTP



Afebrile, Nontoxic Patient:

 • Palpable Rash:

	- Autoimmune Vasculitis (lupus, RA, Sjogren's, GPA, EGPA, Microscopic)

	- Viral (echovirus, coxsackie, measles, Parvovirus)

 • Non-Palpable Rash:

	- ITP

	- APLS

	- HIT

	- ITP

	- Cholesterol embolism

	- Amyloidosis

	- Nutritional deficiency



Work Up:

 • Complete blood count coagulation studies

 • Urinalysis

 • Fecal occult blood test

 • Serology for hepatitis B and C

 • Serum protein electrophoresis, anti-streptolysin O titre

 • Measurement of antinuclear antibodies, antineutrophil cytoplasmic antibodies, rheumatoid factor

 • Serum immunoglobulins & cryoglobulins

 • Skin biopsy

 • Abdominal ultrasound



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